The study objectives are: (1) to determine the effect of pancreas transplantation on hepatic glucose production and glucose turnover rates in Type I diabetic recipients in the basal hypoglycemic states, (2) to evaluate whether successful pancreas transplantation will, over time, improve insulin sensitivity and glucose effectiveness in Type I diabetic recipients, (3) to determine whether changes in substrate utilization, energy expenditure and body composition are due to metabolic changes caused by pancreas transplantation.